The subject of this vote was final passage of a $401.5 billion conference report on the 2004 defense authorization bill (a conference report, which is hashed out in a conference committee, is the final version of a piece of legislation). Progressives voted against final passage based on three concerns they had with the legislation. First, Progressives opposed provisions in the bill which failed to extend full retirement and disability benefits to all of the nation's veterans (as written, the conference report would extend those benefits to some, but not all, U.S. veterans who were wounded in battle while defending the United States). Second, Progressives objected to funding which was included in the conference report to develop new "low-yield" nuclear weapons systems (in contrast to "high-yield" nuclear weapons such as the hydrogen bomb, low-yield weapons would have limited explosive capabilities and could be used to eradicate concentrated targets). Progressives were worried that the development of low-yield nuclear weapons would undermine efforts to ban and dismantle all nuclear weapons. Third, based on their support for protecting endangered species, Progressives voiced opposition to provisions in the conference report which would exempt the Defense Department from the Endangered Species Act and the Marine Mammal Protection Act. Conservatives voted in support of the conference report and, in response to the charges levied by Progressives, argued that the conference report would expand retirement and disability benefits for veterans, would improve, through the development of low-yield nuclear weapons, the ability of the U.S. military to attack terrorists hiding underground (which was the stated purpose of low-yield nuclear weapons), and would allow the Defense Department to conduct weapons testing without the constraints of environmental laws and thereby improve the effectiveness of the military. On an overwhelming 362-40 vote, the conference report on the defense authorization bill was adopted and President Bush signed the measure into law on November 24, 2003.